Projection television sets, particularly rear projection sets, are a popular alternative to picture tube television sets, as they provide relatively large viewable screens that cannot be efficiently produced using conventional picture tubes. Rear projection television sets typically include a casing with a set of internal projection tubes, a mirror, and electronic components for receiving and projecting an image onto a screen assembly mounted on the front of the casing.
Each projection tube projects an image, generally of a single color of light, onto the mirror in the casing which focuses the image onto an inside surface of a lenticular screen and/or fresnel lens included in the screen assembly. The lenticular screen is substantially transparent, thereby allowing the image projected onto its inside surface to be focused and observed from the outside of the television set.
The screen assembly typically includes a frame which supports the lenticular screen and facilitates attachment of the screen assembly to the casing of the television set. To produce the screen assembly, the individual components, i.e. the lenticular screen and the frame, are first made in a conventional manner. The lenticular screen is then substantially permanently attached to the frame, typically using a plurality of capture rails and fasteners. After the lenticular screen is placed over the assembled frame, the capture rails, which are provided in pairs, are placed over opposite edges of the lenticular screen, and then fasteners are driven or inserted through the capture rails and into the frame. The screen assembly may then be attached to the casing, typically after the internal components of the television set, e.g. the mirror, the projection tubes, the electronic components and/or speakers, are installed.
The casing often includes a plurality of mounting tangs attached along a perimeter of an opening in its front panel, e.g. at predetermined locations along the top and side edges of the opening. The frame includes corresponding slots along its back edges adapted to receive the tangs therein, and thereby securely attach the screen assembly to the casing. Alternatively, the frame may include a number of mounting tabs extending out from its outer edges through which screws, bolts and the like may inserted to attach the screen assembly to the casing.
One of the primary complications associated with rear projection television sets is accessing the internal components during final assembly and testing and/or when the television sets are later repaired. In particular, it is often desirable or necessary to adjust or clean the projection tubes and/or mirror, for example, to focus the images projected onto the lenticular screen.
Although a removable access panel may be provided on the back of the casing to provide access, such rear access panels may be limited in size or location due to the placement of the internal components, such as the mirror, or the electronic components. Further, when adjusting the focus of the television set, the image on the outside of the screen must be intermittently viewed to gauge progress. Rear access panels require an assembly or service person to move between the back and the front of the set to first adjust the focus and then view the image, often repeatedly.
Alternatively, service personnel may use an external mirror to facilitate viewing of the screen during adjustment. The mirror is placed at a location in front of the set and angled to allow the image on the screen to be seen in the mirror from the back of the set. This arrangement, however, may be inconvenient, particularly to field service personnel, as it may require a portable mirror and stand that has to be assembled and properly oriented prior to use. Also, the location of the television set may not provide adequate space to effectively use the portable mirror, possibly still requiring service personnel to move at least partially between the back and the sides or front of the television set.
Alternatively, the screen assembly may be detachable from the casing or may be hinged to provide access into the interior of the casing from the front. This arrangement, however, exacerbates the task of focusing, because the lenticular screen is removed from the focal plane of the television set. Thus, the screen assembly must be repeatedly opened and closed, or detached and reattached, to allow the internal components to be adjusted and then allow the image to be viewed after each adjustment.
Another complication with conventional lenticular screen assemblies is the handling of the screen assemblies during manufacturing. Because of the large size of the screens typically desired for projection televisions, the lenticular screen and frame are bulky components which are difficult and awkward to maneuver. During assembly, the lenticular screen and frame may be handled multiple times, increasing the risk of damage to the parts and resulting in slower, less efficient manufacturing.
Accordingly, there is a need for a lenticular screen assembly for projection television sets which minimizes necessary handling of the screen assembly and/or its components during manufacturing.
In addition, there is also a need for a rear projection television set which facilitates access to the interior of the set to adjust, clean or repair the internal components without removing the screen assembly.